Doom · PC · 1993 · Cheat Code
Effect: Makes the player invulnerable to all damage for the rest of the level.
IDDQD — one of the most famous cheat codes in PC gaming history — was built into id Software's Doom from launch as a convenience for players who wanted to explore the game's levels without the pressure of combat. The "ID" prefix tagged every Doom cheat as an id Software command. Typing the code displays the message "Degreelessness Mode On," an id in-joke: "DQD" stood for "Delta-Q-Delta," a mock fraternity for programmers who had withdrawn from (rather than failed) college classes, earning a "Q" grade — so "degreelessness" riffed on never finishing a degree. God Mode became a staple of PC gaming culture and a shorthand term for invincibility far beyond Doom itself.